The purpose of the present invention is to describe a preparation method of activated carbon from fungi with a high CO₂ adsorption potential.

Activated carbon used for commercial purposes is obtained in the processes of carbonisation and activation of materials containing elemental carbon, such as coal, lignite, peat, wood and semi-coke.

There exists an extensive body of literature reports on the preparation methods of coal materials from organic raw materials. The methods are to be recommended since they are economical and sustainable. Please, find below a list of recommended review surveys: SJ . T. Pollard, G.D. Fowler, CJ. Sollar, R. Perry, Low cost adsorbent for waste and wastewater treatment: a review , Science of the Total Environment 1992, 116(1-2), 31-52; O. Ioannidou, A. Zabaniotou, Agricultural residues as precursors for activated carbon production-A review, Renewable and Sustainable Energy Reviews 11 (2007) 1966-2005; J. M. Diasa, M. C. M. Alvim-Ferraza, M. F. Almeidaa, J. Rivera-Utrillab, M. Sanchez-Polob, Waste materials for activated carbon preparation and its use in aqueous-phase treatment: A review, Journal of Environmental Management 85 (2007) 833-846; A. Demirbas, Agricultural based activated carbons for the removal of dyes from aqueous solutions: A review, Journal of Hazardous Materials 167 (2009) 1-9; R. H Hesasa, W. M. A. Wan Dauda, J.N. Sahua, A. Arami-Niyaa, The effects of a microwave heating method on the production of activated carbon from agricultural waste: A review, Journal of Analytical and Applied Pyrolysis 100 (2013) 1-11.

The reports mention the use of pits, husks and straw of different plants as well as wood and cones of various trees. The polish patent application P.386878 describes activated carbon used for electrochemical storage of hydrogen and the method of its preparation. Carbon is obtained from specially prepared taqua nuts from Phytelephas macrocarpa palm trees. Nuts undergo the commonly known processes of pyrolysis, carbonisation and activation at the specific parameters being the essential feature of the invention. Carbon is characterised with an amorphous structure and is made up of a large number of individual graphene layers with a distinct hexagonal structure without fragments orientated in the form of graphite-like crystallites in the area of approximately 2 nm. Micropores in its porous structure do not have a dominant orientation of their spatial structure. Carbon is characterised with a unique ratio between micro- and mesopores, and an unusual proportion between the system of ultramicropores and micropores proper and supermicropores.

Very few papers have been published on the preparation of activated carbon from mushrooms.

Xiao et al. (H. Xiao, H. Peng, S. Deng, X. Yang, Y. Zhang, Y. Li, Preparation of activated Carbon from edible fungi residue by microwave assisted k2CO3 activation Application in reactive black 5 adsorption from aqueous solution, Bioresource Technology 111 (2012) 127-133) produced activated carbon from edible mushrooms, using a solution of K₂CO₃ as the activator. After drying, solid material was exposed to microwave radiation. The obtained activated carbon was an effective sorbent of reactive black 5 from aqueous solutions.

Wang et al. (J. Wang, I. Senkovska, S. Kaskel, Q. Liu. Chemically activated fungi-based porous carbons for hydrogen storage. Carbon 2014; 75; 380-72) used four types of fungi: auriculariales (Auriculariales), shaggy ink caps (Coprinus comatus), shiitake (Lentitus edodes) and Agaricus mushrooms, as substrates in the production of activated carbon. Prior to their use, dried mushrooms were soaked in warm water, rinsed with deionized water to remove all impurities and then dried at 80°C. Clean and dried mushroom samples were carbonised at the temperature of 500°C. Carbonised mushrooms were ground with solid KOH in various weight ratios and exposed to the temperature of 600-750°C. Later, they were treated with an HCl solution, distilled water and dried. Most activated carbons were characterised with the specific surface area greater than 2000 m²/g. The materials were confirmed to be good hydrogen sorbents. The maximum amount of adsorbed hydrogen was 2.4 mass %, under the pressure of 1 bar at -196°C.

Wang et al. (J. Wang, A. Heerwig, M. Lohe, M. Oschatz, L. Borchardt, S. Kaskel, Fungi-based Porous Carbons for CO2 Adsorption and Separation, J. Mater. Chem. 22 (2012), 13911-13913) obtained activated carbons from Agaricus fungi. The initial material was first charred and then ground with a solid KOH in different proportions. The mixtures were carbonised at the temperature of 700°C. The obtained activated carbons had a high specific surface area (up to 1778 m²/g). The materials were characterised with a high CO₂ adsorption (up to 5.5 mmol/g at the temperature of 0°C, under the pressure of 1 bar).

Unexpectedly, it was found that the fruiting body of arboreal fungi - polypores - can be used to produce activated carbon with a high CO₂ adsorption. Contrary to fungi described above, polypores are not edible pests to be eliminated and utilised. Interestingly, they can be a very cheap source of carbon.

The method of preparation of obtaining activated carbon from fungi when an activator or its solution is added to fungi, the mixture is dried, carbonised under an inert atmosphere, rinsed and dried is characterised in that dried polypores are mixed with an aqueous solution of the activator or that moistened polypores are mixed with the solid activator at the weight ratio of 1 : 0.1-5. KOH and/or NaOH and/or ZnCl₂ and/or Na₂CO₃ and/or K₂CO₃ are used as the activators. The mixture is left for 0 - 24 h and carbonised at the temperature of 400 - 1000°C. After cooling, the product is rinsed with distilled water to obtain neutral pH, treated with hydrochloric acid, again rinsed with distilled water to obtain neutral pH and dried.
The process is conducted under an inert atmosphere flow of 0.5 - 50 1/h. Nitrogen or any noble gas can be used at the inert gas.

The invented method enables production of activated carbon from polypores with a high specific surface area and CO₂ sorption. The essential feature of the invention is presented more in-depth in the examples below.

The birch polypore (Piptoporus betulinus) was dried at the temperature of 200 °C for 24 h. It was crushed and ground in a mortar to obtain a powder. 5g of dried and ground birch polypore (Piptoporus betulinus) was treated with a saturated KOH solution in the carbon: modifier mass ratio of 1:1 was left for 1 h. Then, it was dried at the temperature of 200°C for 19 h. The powdered material was soaked in a combustion tube furnace at 750°C, under nitrogen flow of 181/h. After cooling, the product was treated with distilled water to remove KOH residues and to obtain neutral pH, treated with 1 dm³/mol HCl, and rinsed again with distilled water to obtain neutral pH. The obtained product was dried at the temperature of 200°C.

The obtained activated carbon had the specific surface area of 1672 m²/g, capable of CO₂ sorption of 5.42 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.

The procedure was the same as that in Example 1, except for the fact that the lumpy bracket (Trametes gibbosa) was used as the raw material. After drying, it was ground with a solid K₂CO₃ at the carbon : modifier mass ratio of 1:5. The mixture was left for 24 h and soaked in a furnace at the temperature of 1000°C, under argon flow of 11/h.

The obtained activated carbon had the specific surface area of 2072 m²/g, capable of CO₂ sorption of 5.7 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.

The procedure was the same as that in Example 1, except for the fact that the lumpy bracket (Trametes gibbosa) was used as the raw material. After drying, it was ground with a solid NaOH at the polypore : modifier mass ratio of 1:0.1. The mixture was left for 10 h and soaked in a furnace at the temperature of 400°C, under helium flow of 0.51/h.

The obtained activated carbon had the specific surface area of 972 m²/g, capable of CO₂ sorption of 3.7 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.

The procedure was the same as that in Example 1, except for the fact that the raw material after drying was moistened with water (5g of the material, 5 ml of water). Then, solid Na₂CO₃ and KOH were added at the polypore: Na₂CO₃ KOH mass ratio of 1:1:1.5. The mixture was left for 0 h and soaked in a furnace at the temperature of 950°C, under nitrogen flow of 501/h.

The obtained activated carbon had the specific surface area of 1972 m²/g, capable of CO₂ sorption of 4.8 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.

The procedure was the same as that in Example 1, except for the fact that the raw material after drying was moistened with water (5g of the material, 5 ml of water). Then, solid Na₂CO₃ and KOH were added at the polypore: ZnCl₂ : KOH mass ratio of 1:3:1. The mixture was left for 15 h and soaked in a furnace at the temperature of 650°C, under argon flow of 221/h.

The obtained activated carbon had the specific surface area of 1178 m²/g, capable of CO₂ sorption of 3.3 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.

The procedure was the same as that in Example 1, except for the fact that K₂CO₃ was used as the activator at the polypore: modifier mass ratio of 1:3.5. The mixture was left for 12 h and soaked in a furnace at the temperature of 700°C, under helium flow of 5 1/h. After cooling, the product was rinsed with distilled water to obtain neutral pH (no hydrochloric acid treatment was applied).

The obtained activated carbon had the specific surface area of 742 m²/g, capable of CO₂ sorption of 3.5 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.

The procedure was the same as that in Example 1, except for the fact that the lumpy bracket (Trametes gibbosa) was used as the raw material. After drying, it was ground with a solid ZnCl₂ at the polypore:modifier mass ratio of 1:5. The mixture was left for 24 h and soaked in a furnace at the temperature of 1000°C, under nitrogen flow of 45 1/h.
The obtained activated carbon had the specific surface area of 992 m²/g, capable of CO₂ sorption of 3.7 mmol/g, at the temperature of 0°C, under the pressure of 1 bar.